1. Field of the Invention
The present invention relates to a transmission apparatus, and more particularly, to a serial transmission apparatus and the signal transmission method thereof.
2. Description of the Related Art
The communication between controllers or between a controller and a peripheral device can be divided into classifications of parallel communication and serial communication, where the serial communication needs only three transmission wires (i.e., a clock signal wire, a data signal wire and a strobe signal wire) to complete the transmission. Usually, the transmission is done in such a manner that one data bit per clock cycle is serially transmitted to the destination device. When all serial data have been received by corresponding serially-connected data transmission apparatuses, the controller generates a strobe signal to latch a plurality of parallel output signals.
Serial transmission communication can be applied to a wide variety of electronic devices, such as traffic signs or large-scale advertisement boards, by using LEDs as their light source. Large-scale advertisement boards are often comprised of tens of thousands LEDs, and thus need a plurality of serially-connected data transmission apparatuses to control the lighting information of the LEDs. Serial transmission can also be applied to local dimming technology to control LED backlight in a local area. FIG. 1A shows a block diagram of a conventional serial transmission apparatus and FIG. 1B shows the circuit diagram of each data transmission apparatus. Referring to FIG. 1B, the data transmission apparatus 10 has a clock signal CLK, a strobe signal LAH, a data input end SDI, a data output end SDO, and a plurality of parallel output ends OUT1, OUT2, . . . , OUTN. The data transmission apparatus 10 includes a shift register 101 and a latch 102. The shift register 101 includes an N-stage register for receiving serially-connected input data, where the first stage of the shift register 101 is connected to the input end SDI, and the last stage thereof is connected to the output end SDO. When a clock signal arrives at the clock end CLK, the shift register 101 shifts serial input data from SDI by one bit to the next stage of the shift register 101. The parallel output signals of the shift register 101 are latched in the corresponding latch 102 when the strobe signal LAH is enabled, and each output stage of the latch 102 is connected to corresponding output ends OUT1, OUT2, . . . , OUTN.
Referring to FIG. 1A, the serial transmission apparatus 11 includes four serially-connected data transmission apparatuses 131-134. Each of the serially-connected data transmission apparatuses 131-134 individually receives an input signal 141-144 and a clock signal, and individually provides one output signal 151-154. The data signal 141, clock signal and strobe signal received by the first data transmission apparatus 131 are provided by a controller 12. Because the output end of each data transmission apparatus 131-133 is coupled to the input end of the next data transmission apparatus 132-134, after the serial data signal output by the controller 12 is received by the first data transmission apparatus 131, the serial data signal propagates through each data transmission apparatus until it reaches the output end SDO. FIG. 1C shows waveforms of input and output signals of the serially-connected data transmission apparatus 11. Because each data transmission apparatus 131-134 includes a shift register 101, it can store N-bit input data. When the Nth clock signal arrives at the clock end CLK, N data bits are stored in the shift register 101 of the first data transmission apparatus 131. Subsequently, when the 2Nth clock signal arrives at the clock end CLK, the N data bits are stored in the shift register 101 of the first and second data transmission apparatuses 131, 132. Finally, when the 4Nth clock signal arrives at the clock end CLK, the N data bit are stored in the shift register 101 of each data transmission apparatus 131-133. After the strobe signal LAH is triggered, the data bit stored in the shift register is synchronously latched in corresponding latch 102, and then output in parallel to output ends OUT1, OUT2, . . . , OUTN of the corresponding data transmission apparatus 131-133. As mentioned above, the conventional serial transmission apparatus 11 can transmit larger amounts of data by increasing the number of serially-connected data transmission apparatuses.
However, if one element of the serial transmission apparatus 11 is out of order, the serial transmission data is held and fails to reach the output end. For example, when the serial transmission apparatus is applied to a large-scale advertisement board, any failure in any stage of the serial transmission apparatus will result in an incomplete display and the image thereon will be difficult to recognize. More importantly, if the serial transmission apparatus is applied to a traffic sign or a transaction display device, a failure in serial transmission could result in injury or loss of property. In addition, when a serial transmission is used to adjust an LED backlight module, any malfunction in the transmission apparatus may result in an entire failure of the LED backlight module. To address such issues, the present invention provides a serial transmission apparatus and method thereof to avoid any interruption in transmission.